1. Field of the Invention
This invention relates to a multi-band antenna and more particularly to a dual band antenna which automatically operates at two different frequency bands.
2. Description of the Related Art
Due to overcrowding of the cellular telephone infrastructure, the cellular telephone industry is looking for ways to create room for the ever-increasing number of cellular telephone subscribers. The creation of room for additional cellular telephone subscribers must be accomplished without degrading the quality of the audio signal or compromising the reliability or integrity of the wireless connection. Much research has been done in this area and several possible solutions have been suggested. One solution is to switch from the existing analog to digital systems, which has been proven to create better performance in terms of quality of signal and speed. In other words, digital technology provides the carrier with the ability to fit more cellular conversations in a given band width as compared to the analog system.
Another solution for the problem described above is to create more room in terms of frequency band width. The FCC has allocated more frequency bands to be used for cellular telephone conversations. This new band of spectrum is located around the 2 Ghz band and is used for telephone systems such as PCS band (Personal Communication System), DCS 1800, and DECT. This higher band was chosen primarily because of the availability of bands close to the original 800-900 MHz.
Unfortunately, the changes outlined above have created additional problems in the industry. The cellular telephone infrastructure in the United States and in other countries was originally built for the 800 to 900 MHz frequencies. Now, with the advent of digital systems and the use of the new higher frequencies, a dilemma arises in switching over to the new system. Many geographical areas will add the higher frequencies and the digital systems as a second system and will keep the original analog system operational. Some locations will stay with the old analog systems longer than others; therefore, to ensure full coverage, the user will either have to carry two telephones or purchase a "Multi-Mode" telephone. A "Multi-Mode" telephone is a telephone that will automatically switch from one system to the other depending upon the way it is programmed.